Photoelectronic device and production method of the same

ABSTRACT

A photoelectronic device capable of maintaining the degree of freedom in designing for dealing with design changes and responding to producing a variety of kinds in a small amount, and the production method are provided: wherein a light emitting element for emitting a light to be a clock signal, a semiconductor chip provided with light receiving portions for receiving the light, and an optical waveguide sheet formed to be a sheet, wherein an outer circumference of a core is covered with a clad, adhered to said semiconductor chip are provided; and the optical waveguide sheet is configured to be irradiated at a light incident portion of a core with a light from the light emitting element and includes one or more T-shaped branch having a vertical opening portion having a vertical inner wall, which is vertical with respect to the direction within a surface of the optical waveguide sheet and becomes a mirror surface for dividing and reflecting the light, and a sloping opening portion having a sloping inner wall, which has an inclination with the optical waveguide direction of the core and becomes a mirror surface for reflecting the light to the direction being out of the surface of the optical waveguide sheet so as to be connected to a light receiving portion at a connection position of each of the lights and each of the light receiving portions.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2004-221984 filed in the Japanese Patent Office on Jul.29, 2004, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectronic device and theproduction method and, particularly, relates to a photoelectronic deviceconfigured that a light emitting element for emitting a light to be aclock signal is optically connected to a semiconductor chip having anelectron circuit including a light receiving portion by an opticalwaveguide sheet, and the production method.

2. Description of the Related Art

Demands for portable electronic apparatuses, such as a digital videocamera, a digital cellular phone and a notebook personal computer, to bemore compact, thinner and lighter have only become stronger and, torespond thereto, a reduction in size by 70% has attained in a VLSI andother semiconductor devices in three years.

On the other hand, a package form of semiconductor devices has alsodeveloped from a lead-inserted type, such as a DIP (Dual InlinePackage), to a surface mounting type and a flip-chip mounting type,furthermore, to a complex form called a system-in-package (SIP), whereina semiconductor chip provided with an active element is packaged with apassive element.

As explained above, development of semiconductor techniques isremarkable, and particularly in the field of a CPU and high-speed logicLSI, the clock frequency has already exceeded GHz order.

Wiring of a signal exceeding GHz suffers from a lot of disadvantages tobe solved inside and outside the LSI, which have not been any problemsbefore, and solution of these disadvantages is a very significantelement in recent semiconductors becoming furthermore higher inintegration and higher in speed.

The disadvantages are signal distortion (signal integrity), a frequencylimit of electric wiring, a loss of wiring, delay of wiring, radiationfrom wiring, a signal skew, and an increase of power consumptionrelating to driving wiring, etc.

Particularly, in recent years, a skew (timing difference) of a clock tobe supplied in an LSI chip or to different LSIs has become a problem.For example, time of 1 digit of 1 GHz is 500 ps, and time of rising andfalling is about several 10 ps to 200 ps or shorter, while in wiring ona general dielectric, wherein ε=4 or so, a rough propagation speed of anelectric signal is 67 ps/cm, which has reached an unignorable range withrespect to the rising time.

Thus, lots of attempts have been made to suppress a wiring skew by usingcompletely equal-length wiring also for wiring on a mounting substrateor on an LSI, and dividing a clock to wiring having an H-shape called anH bar to suppress a wiring skew.

When performing clock dividing by electric wiring of the related art,there was a disadvantage that a power consumption became large because awiring load was always driven by a clock frequency, furthermore,waveform shaping was performed at each dividing point.

To overcome the above disadvantages, instead of electric wiring using ametal, such as aluminum and copper, there is a proposal of using opticsfor wiring and dividing a clock.

For example, the non-patent article (Shiou Lin Sam, Anantha Chandrakasanand Duane Boning, Variation Issues in On-Chip Optical ClockDistribution, Sixth International Workshop on Statistical Methodologiesfor IC Processes, Devices, and Circuits, Kyoto, Japan, June 2001)discloses a technique of obtaining a wiring plate having an opticalclock tree by forming an optical waveguide on a silicon substrate andprocessing the same by using a mask in a semiconductor process for eachLSI.

However, in the above method of forming clock wiring layers successivelyby a semiconductor process on a substrate, such as silicon, ceramic oran organic substrate, there is a trouble that design and a maskcorresponding to a specific LSI have to be made and processing has to beperformed for that each time.

Also, since all production processes are performed sequentially, theentire TAT (turn around time) becomes long and it is hard to deal withsmall changes.

SUMMARY OF THE INVENTION

It is desired to solve disadvantages that it is hard to maintain thedegree of freedom in designing for dealing with design changes and thatit is difficult to respond to producing a variety of kinds in a smallamount.

According to the present invention, there is provided a photoelectronicdevice, comprising a light emitting element for emitting a light to be aclock signal; a semiconductor chip provided with light receivingportions for receiving the light; and an optical waveguide sheet formedto be a sheet, wherein an outer circumference of a core is covered witha clad, and adhered to the semiconductor chip; wherein the opticalwaveguide sheet is irradiated at a light incident portion of the corewith the light from the light emitting element; the optical waveguidesheet is provided with one or more T-shaped branch, and at each T-shapedbranch is provided with a vertical opening portion having a verticalinner wall being vertical with respect to the direction within a surfaceof the optical waveguide sheet, and the vertical inner wall serves as amirror surface for dividing, reflecting and guiding the light to twodifferent directions; and a sloping opening portion having a slopinginner wall having an inclination with the optical waveguide direction ofthe core is provided at a position of connecting each of the dividedlights to each of the light receiving portions, and the sloping innerwall serves as a mirror surface for reflecting the light to thedirection being out of the surface of the optical waveguide sheet to beconnected to the light receiving portion.

The above photoelectronic device has a light emitting element foremitting a light to be a clock signal, a semiconductor chip providedwith light receiving portions for receiving the light, and an opticalwaveguide sheet formed to be a sheet, wherein an outer circumference ofa core is covered with a clad, and adhered to the semiconductor chip.

Here, the optical waveguide sheet has the configuration that the lightfrom the light emitting element is irradiated at a light incidentportion of the core with, it is provided with one or more T-shapedbranch, at each T-shaped branch is provided with a vertical openingportion having a vertical inner wall being vertical with respect to thedirection within a surface of the optical waveguide sheet, and thevertical inner wall serves as a mirror surface for dividing, reflectingand guiding the light to two different directions, furthermore, asloping opening portion having a sloping inner wall having aninclination with the optical waveguide direction of the core is providedat a position of connecting each of the divided lights to each of thelight receiving portions, and the sloping inner wall serves as a mirrorsurface for reflecting the light to the direction being out of thesurface of the optical waveguide sheet to be connected to the lightreceiving portion.

According to the present invention, there is provided a productionmethod of a photoelectronic device for producing a photoelectronicdevice including a light emitting element for emitting a light to be aclock signal, a semiconductor chip provided with light receivingportions for receiving the light, and an optical waveguide sheet fordividing the light to two or more and guiding the same to be connectedto the light receiving portions at positions of connecting to the lightreceiving portions, comprising the steps of: forming a first clad on adummy substrate, forming a core on the first clad to be a pattern havingone or more T-shaped branch and forming a second clad to cover the core,thereby forming an optical waveguide sheet formed to be a sheet whereinan outer circumference of the core is covered with the clad; forming ata position of the T-shaped branch on the optical waveguide sheet avertical opening portion having a vertical inner wall, which is verticalwith respect to the direction within the surface of the opticalwaveguide sheet and becomes a mirror surface for dividing and reflectingthe light to two different directions; forming at a position ofconnecting the light to the light receiving portion on the opticalwaveguide sheet a sloping opening portion having a sloping inner wall,which has an inclination with the optical waveguide direction of thecore and becomes a mirror surface for reflecting the light to thedirection being out of the surface of the optical waveguide sheet so asto be connected to the light receiving portion; releasing the opticalwaveguide sheet from the dummy substrate; aligning the optical waveguidesheet with the light receiving portion and adhering to the semiconductorchip; and mounting the light emitting element by arranging the same, sothat a light from the light emitting element irradiates a light incidentportion of the core.

The above production method of a photoelectronic device is for producinga photoelectronic device having a light emitting element for emitting alight to be a clock signal, a semiconductor chip provided with lightreceiving portions for receiving the light, and an optical waveguidesheet for dividing the light to two or more and guiding the same to beconnected to the light receiving portions at positions of connecting tothe light receiving portions.

First, a first clad is formed on a dummy substrate, a core is formed onthe first clad to be a pattern having one or more T-shaped branch, and asecond clad is formed to cover the core, thereby an optical waveguidesheet formed to be a sheet, wherein an outer circumference of the coreis covered with the clad, is formed.

Next, a vertical opening portion having a vertical inner wall, which isvertical with respect to the direction within the surface of the opticalwaveguide sheet and becomes a mirror surface for dividing and reflectingthe light to two different directions, is formed at a position of theT-shaped branch on the optical waveguide sheet.

Next, a sloping opening portion having a sloping inner wall, which hasan inclination with the optical waveguide direction of the core andbecomes a mirror surface for reflecting the light to the direction beingout of the surface of the optical waveguide sheet so as to be connectedto the light receiving portion, is formed at a position of connectingthe light to the light receiving portion on the optical waveguide sheet.

Next, the optical waveguide sheet is released from the dummy substrate,and the optical waveguide sheet is aligned with the light receivingportion and adhering to the semiconductor chip.

Next, the light emitting element is arranged at a predetermined positionfor mounting, so that a light from the light emitting element irradiatesa light incident portion of the core.

A photoelectronic device of the present invention is configured byputting an optical waveguide sheet for dividing a clock and asemiconductor chip together, and capable of maintaining the degree offreedom in designing for dealing with design changes and responding toproducing a variety of kinds in small amounts.

The production method of a photoelectronic device of the presentinvention is to form a photoelectronic device by putting an opticalwaveguide sheet for dividing a clock and a semiconductor chip together,by which it is possible to maintain the degree of freedom in designingfor dealing with design changes and it is possible to produce byresponding to producing a variety of kinds in small amounts.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the attached drawings, in which:

FIG. 1A is a schematic sectional view and FIG. 1B is a plan view of aphotoelectronic device according to a first embodiment of the presentinvention;

FIG. 2 is a schematic view for explaining the configuration of avertical opening portion;

FIG. 3A to FIG. 3C are sectional views showing a production procedure ofa production method of the photoelectronic device according to the firstembodiment of the present invention;

FIG. 4A and FIG. 4B are sectional views showing a production procedureof the production method of the photoelectronic device according to thefirst embodiment of the present invention;

FIG. 5A to FIG. 5C are sectional views showing a production procedure ofthe production method of the photoelectronic device according to thefirst embodiment of the present invention;

FIG. 6A to FIG. 6C are sectional views showing a production procedure ofthe production method of the photoelectronic device according to thefirst embodiment of the present invention;

FIG. 7A and FIG. 7B are sectional views showing a production procedureof the production method of the photoelectronic device according to thefirst embodiment of the present invention;

FIG. 8 is a schematic sectional view of a photoelectronic deviceaccording to a second embodiment of the present invention; and

FIG. 9 is a schematic sectional view of a photoelectronic deviceaccording to a third embodiment of the present invention

DESCRIPTION OF THE PREFERRED EMBODIMENT

Below, embodiments of a photoelectronic device configured that a lightemitting element for emitting a light to be a clock and a semiconductorchip having an electronic circuit including a light receiving portionare optically connected by an optical waveguide sheet, and theproduction method will be explained with reference to the drawings.

First Embodiment

FIG. 1A is a schematic sectional view and FIG. 1B is a plan view of aphotoelectronic device according to a first embodiment of the presentinvention.

A light emitting element 20 for emitting a light to be a clock signal,such as a semiconductor laser diode, is mounted on a surface of asemiconductor chip 10, furthermore, on the surface of the semiconductorchip 10, an optical waveguide sheet 30 formed to be a sheet shape,wherein an outer circumference of a core 30 b stretching in stripes inthe optical waveguide direction is covering with a clad 30 a, is adheredby an adhesive layer 31.

The semiconductor chip 10 is formed with an electronic circuit includinga light receiving portion 11, such as a photodiode.

The light emitting element 20 is mounted on the semiconductor chip 10 soas to be connected to pads of the semiconductor chip 10 via bumps 21.

The optical waveguide sheet 30 is irradiated at its light incidentportion of the core 30 b with a light from the light emitting element 20from a side surface of the optical waveguide sheet 30, divides the lightto two or more (16 in the figure) at one or more (15 in the figure)T-shaped branch S provided on the core, and guides the same.

The semiconductor chip 10 has the configuration that a plurality oflight receiving portions 11 are provided, sloping opening portions Pihaving sloping inner walls with respect to the optical waveguidedirection of the core 30 b are provided at positions where the dividedlights are connected to the light receiving portions 11, and the slopinginner walls function as mirror surfaces (MRa and MRb) to reflect thelights to the direction being out of the surface of the opticalwaveguide sheet 30 so as to be connected to the light receiving portions11, so that the lights divided at the optical waveguide sheet 30 arerespectively connected to the light receiving portions 11.

The inclination of the sloping inner walls of the sloping openingportions Pi is, for example, 45° with respect to the optical waveguidedirection of the core 30 b. The sloping directions of the mirrorsurfaces (MRa and MRb) are different in accordance with difference ofthe stretching direction of the core.

The above T-shaped branch S will be explained. FIG. 2 is a schematicview for explaining the configuration of a vertical opening portion.

The T-shaped branch S is a branching point in the clad 30 a, where acore 30 b is formed to be a pattern, so that one waveguide is branchedto two and an angle made by the branched two waveguide directionsbecomes 180°.

At the T-shaped branch S, a vertical opening portion Pv having verticalinner walls with respect to the direction within the surface of theoptical waveguide sheet is provided, and the vertical inner wallsfunction as mirror surfaces (MRc and MRd) to divide, reflect and guidethe light L to two different directions. The mirror surfaces (MRc andMRd) are surfaces having an inclination angle of, for example, 45° withrespect to the incident direction and emitting direction of the T-shapedbranch S, respectively.

The optical waveguide sheet is translucent to a wavelength of a light tobe used and, for example, a polyimide resin, polyolefin resin,polynorbornene resin, acrylic resin and epoxy resin, etc. or fluorideand other organic based materials may be used.

The light receiving portion 11 of the semiconductor chip 10 is composedof a photodiode, etc. and, furthermore, for example, an amplifier isprovided near that on the semiconductor chip 10 and a clock signal of anincident light is demodulated to an electric clock signal.

To open the pads on the semiconductor chip 10, pad opening portions 30 ppenetrating the optical waveguide sheet 30 and the adhesive layer 31 areformed. The pad opening portions 30 p penetrating the optical waveguidesheet 30 are formed only on a region of not guiding a light.

On the optical waveguide sheet 30 of the photoelectronic device asabove, distances of guiding lights from a position of a light incidentportion of the core 30 b to positions of connecting the lights to lightreceiving portions 11 are preferably equal in all paths that the lightsdivided to two or more are guided.

By attaining completely equal-length wiring in optical wiring forsupplying a clock as explained above, a skew at the time of dividing aclock signal to a plurality of light receiving portions 11 can be almostsuppressed.

According to the photoelectronic device according to the presentembodiment explained above, it is configured by putting an opticalwaveguide sheet for dividing a clock and a semiconductor chip together,and capable of maintaining the degree of freedom in designing fordealing with design changes and responding to producing a variety ofkinds in small amounts. Particularly, by attaining completelyequal-length wiring in optical wiring for supplying a clock, a skew atthe time of dividing a clock signal to a plurality of light receivingportions can be almost suppressed.

Also, in the case of using a Y-shaped branch for branching a light,while it also depends on a refractive index difference between the coreand the clad, when assuming that a curvature radius able to be curvedwithout a loss by entire reflection is 3 to 5 mm or so in a normalorganic waveguide material and a size of a normal LSI is 10 mm×10 mm orso, it has been hard to adapt to the case of performing signal imputingat a large number of points as 16 or more when branching a light in anH-tree shape. On the other hand, the photoelectronic device according tothe present embodiment as above uses T-shaped branch and is capable ofdealing with signal inputting at a large number of points as 16 or more.

Next, a production method of a photoelectronic device according to thepresent embodiment will be explained.

A semiconductor chip and light emitting element can be produced by usingwell known processes.

As a method of forming an optical waveguide sheet, first, as shown inFIG. 3A, a stacked body of a titanium layer and a copper layer is formedon a surface of a dummy substrate 40 made by silicon or glass, etc., forexample, by the electron beam evaporation method or the sputteringmethod, etc. to obtain a release layer 41. Alternately, a release layer41 may be also obtained by forming a silicon oxide layer by the CVD(Chemical Vapor Disposition) method or the sputtering method. In thiscase, silicon, etc. is used for the dummy substrate 40.

Next, as shown in FIG. 3B, a resin layer having a first refractive indexis formed by a polyimide resin, etc., for example, by the spin coatingmethod or the printing method and cured by performing curing processingto obtain a first clad 30 a.

Next, as shown in FIG. 3C, a photosensitive resin layer having a secondrefractive index, which is higher than the first refractive index, isformed, for example, by photosensitive polyimide, etc., performingexposure by using a patterning mask and, furthermore, performing curingprocessing to form a core 30 b.

For simplifying the mounting, when assuming multimode propagation, asuitable thickness and width of the core 30 b are about 5 to 50 μm and asuitable thickness of the clad 30 a is about ¼ to ½ of that of the core30 b.

Next, as shown in FIG. 4A, in the same way as the above, a resin layerhaving a first refractive index is formed by a polyimide resin, etc.,for example, by the spin coating method or the printing method, heatingreflow is performed if necessary, and curing processing is performed forcuring to form a first clad 30 a.

As explained above, an optical waveguide sheet 30, wherein an outercircumference of the core 30 b is covered by the clad 30 a, is formed.

FIG. 4B shows a section in parallel with the stretching direction of thecore in the state shown in FIG. 4A and is a section in the directionbeing perpendicular to that in FIG. 4A. Steps after this will beperformed along the section in this direction.

Next, as shown in FIG. 5A, a metal mask MM in a pattern having anopening at a region for forming the T-shaped branch is formed. This canbe formed by forming, for example, a metal layer allover the surface,forming a pattern of a resist film in a pattern having an opening at aregion for forming the T-shaped branch by the photolithography step, andusing it as a mask for etching the metal layer.

Next, the metal mask MM is used as a mask for performing anisotropic dryetching, such as the RIE (reactive ion etching), vertically with respectto the optical waveguide sheet 30, and a vertical opening portion Pv isformed on the optical waveguide sheet 30. At this time, to enhance theanisotropy, a step etching for repeating stacking of a protective filmfor protecting an etching side walls and etching alternately may beperformed. Also, it is preferable to apply a method of lowering a gaspressure of an etching atmosphere or maintaining a low temperature, etc.As to a kind of gas at this time, by mixing a fluorocarbon based gaswith O₂ and H₂, etc. as additives or by mixing with an inert gas, suchas Ar and Xe, generation of etching residual can be prevented at thesame time.

From the above steps, a pattern of a vertical opening portion Pv isformed, so that the vertical inner walls of the vertical opening portionPv become mirror surfaces (MRc and MRd) for dividing, reflecting andguiding a light guided through the core 30 b to two differentdirections.

After the above step, the metal mask MM is released.

Next, as shown in FIG. 5B, a resist film R1 in a pattern having openingsat positions of connecting lights to light receiving portions is formedon the optical waveguide sheet 30 by the photolithography processing,and by using the resist film R1 as a mask, anisotropic etching, such asRIE (reactive ion etching), is performed by inclining, for example, byabout 45° with respect to the optical waveguide sheet 30. As a result, asloping opening portion Pi having an inclination (for example, 45°) withthe optical waveguide direction of the core 30 b and having a slopinginner wall to be a mirror surface MRa for reflecting a guided light tothe direction being out of the surface of the optical waveguide sheet 30and connecting the same to a light receiving portion is formed.

After the above step, the resist film R1 is released.

Next, as shown in FIG. 5C, on portions, wherein the stretching directionof the core is different from that in the sloping opening portion Pihaving a sloping inner wall to be the mirror surface MRa, a resist filmR2 in a pattern having openings at positions of connecting lights tolight receiving portions is formed by photolithography processing, andby using the resist film R2 as a mask, anisotropic etching, such as RIE(reactive ion etching), is performed by inclining, for example, by about45° with respect to the optical waveguide sheet 30. As a result, asloping opening portion Pi having a sloping inner wall to be a mirrorsurface MRb having an inclination (for example, 45°) with respect to theoptical waveguide direction of the core 30 b but in the differentdirection from that of the sloping opening portion Pi having a slopinginner wall to be the mirror surface MRa is formed.

After the above step, the resist layer R2 is released.

Next, as shown in FIG. 6A, an adhesive thermal release sheet 50, whichcan be released at a specific temperature, is adhered to the surface ofthe optical waveguide sheet 30, and a boundary face of the release layer41 and the clad 30 a of the optical waveguide sheet 30 is released.

The thermal release sheet is configured, for example, by dispersing foamcapsules in an adhesive agent on a PET film and, for example, REVALPHAmade by Nitto Denko Corp., etc. may be used. For example, it can beeasily removed by heating the PET film to 70° C. to 150° C.

In the case of using as a release layer 41 a stacked body of a titaniumlayer and a copper layer, it is released by immersing the opticalwaveguide sheet 30 supported by the above thermal release sheet 50 inacid, such as hydrochloric acid. Alternately, in the case of using asilicon oxide layer as the release layer 41, the optical waveguide sheet30 supported by the above thermal release sheet 50 is immersed in acid,such as fluorinated acid or buffered fluorinated acid to dissolve therelease layer 41.

Next, as shown in FIG. 6B, on the semiconductor chip 10 formed withlight receiving portions 11 on its surface in advance, the opticalwaveguide sheet 30 is adhered by aligning the positions of the mirrorsurfaces (MRa and MRb) of the sloping opening portion Pi with thepositions of the light receiving portions 11 via an adhesive sheet(adhesive layer) 31 being translucent to a wavelength of the light to beused.

Next, as shown in FIG. 6C, the thermal release sheet 50 is released, andthe optical waveguide sheet 30 is transferred on the semiconductor chip10.

After this, in accordance with need, pad opening portions (not shown)for penetrating the optical waveguide sheet 30 and the adhesive layer 31are formed for opening the pads of the semiconductor chip 10. They canbe formed by forming the pads on the semiconductor chip 10 side andirradiating a laser beam, such as CO₂ laser and excimer laser. At thistime, the pads become stoppers of the laser beam.

Next, as shown in FIG. 7A and FIG. 7B, bumps 21, such as gold bumps, areformed on the light emitting element 20, such as laser diode, forexample, by wire bonding, etc. in advance, and mounting them on theadhering surface of the optical waveguide sheet 30 of the semiconductorchip 10. In the drawings, illustration of the opening portions havinginner walls to be mirror surfaces is omitted.

Here, the mounting portion of the semiconductor chip 10 is pre-coatedwith soldering 22 by the printing method, etc. and the light emittingportion of the light emitting element 20 is aligned with the lightincident portion of the core for mounting. At this time, the mountingaccuracy can be improved by using a head having a heater for meltingsoldering by heating, holding after turning off the heater until coolingand removing the heater.

A height of the gold bumps 21 and a thickness of the pre-coating of thesoldering 22 are determined in accordance with a position of the core ofthe optical waveguide sheet for aligning.

Since the gold bumps 21 do not dissolve, the bumps 21 function asspacers, so that a height of the light emitting element 20 can bedetermined by the height of the bumps 21 and high accuracy can beconstantly secured.

As a method of mounting the light emitting element 20 other than theabove, a method of forming bumps obtained by coating copper cores bysoldering on the light emitting element side, forming a pre-coating ofsoldering on the semiconductor chip side and mounting as a flip chip,and a method of forming a spacer by nickel plating, etc. on any one ofthe light emitting element and the semiconductor chip, and mounting as aflip chip by soldering bumps or soldering pre-coating may be used.

According to the production method of the photoelectronic deviceaccording to the above present embodiment, it is configured by puttingan optical waveguide sheet for dividing a clock and a semiconductor chiptogether, and capable of maintaining the degree of freedom in designingfor dealing with design changes and responding to producing a variety ofkinds in small amounts. Particularly, by attaining completelyequal-length wiring in optical wiring for supplying a clock, a skew atthe time of dividing a clock signal to a plurality of light receivingportions can be almost suppressed.

Furthermore, it is possible to always produce a large amount of films tobe the base of the optical waveguide sheet formed as above for dividinga light to be a clock signal, and it is possible to form a slopingopening portion having a sloping inner wall to be a mirror surface atany position in the post-processing. Therefore, even if design of theLSI itself is changed or there are many kinds of LSI having differentspecifications, it is possible to respond to that each time.

As a result, it is possible to suppress the production cost, reduce thedeveloping period and TAT, and develop an LSI, wherein a skew issuppressed.

In the production method of the photoelectronic device according to theabove present embodiment, an example of producing an optical waveguidesheet to be a base on a dummy substrate, such as silicon, by a stepwiseprocedure was explained, but there is also a method of collectivelyproducing by preparing rolls of a polyimide film to be a base, andapplying a core material, for example, by the roll-to-roll processingand patterning. A furthermore large cost reduction can be attainedthereby.

Second Embodiment

FIG. 8 is a schematic sectional view of a photoelectronic deviceaccording to the second embodiment of the present invention.

It is configured that a semiconductor chip 10 adhered to an opticalwaveguide sheet 30 and a light emitting element are mounted on aninterposer 60, and a light from the light emitting element 20 isirradiated from the side surface of the optical waveguide sheet 30 tothe core. Other configuration than that is substantially the same asthat of the first embodiment.

Namely, the light emitting element 20, such as a semiconductor laserdiode, for emitting a light to be a clock signal is mounted on thesurface of the semiconductor chip 10 and, further thereon, the opticalwaveguide sheet 30 formed to be a sheet, wherein an outer circumferenceof the core 30 b stretching in stripes in the optical waveguidedirection is covered with a clad 30 a, is adhered to the semiconductorchip 10 by an adhesive layer 31.

The semiconductor chip 10 is formed with an electronic circuit includinga light emitting portion 11, such as photodiode.

Also, pad opening portions for penetrating the optical waveguide sheet30 and the adhesive layer 31 are formed for opening pads of thesemiconductor chip 10, and bumps 12 are formed to be connected to thepads.

On the interposer 60 formed by stacking a first resin layer 61, a secondresin layer 62 and a third resin layer 63 and forming a wiring pattern64 by penetrating the layers and the boundary faces, a semiconductorchip 10 adhered to the optical waveguide sheet 30 is mounted via thebumps 12.

Also, on the same surface of the interposer 60 as the surface mountedwith the semiconductor chip 10, the light emitting element 20 ismounted.

On the opposite surface of the surface mounted with the semiconductorchip 10 of the interposer 60 is formed with bumps 65 and mounted onstill another mounting substrate for use.

As the interposer 60, all kinds of organic wiring substrates, such as aso-called FR-4 substrate, FR-5 substrate, BT-resin substrate, polyimidesubstrate, and ceramic wiring substrates, such as alumina and glassceramic, can be used.

On the other hand, laser diode to be a light source of a light clock ismounted, for example, on an end portion of the optical waveguide sheetand being close to the core, so that a light is effectively irradiatedto the core of the optical waveguide, and a laser driver for driving thelaser diode is mounted close to that on the interposer 60.

According to the photoelectronic device according to the above presentinvention, it is configured by putting an optical waveguide sheet fordividing a clock and a semiconductor chip together, and capable ofmaintaining the degree of freedom in designing for dealing with designchanges and responding to producing a variety of kinds in small amounts.Particularly, by attaining completely equal-length wiring in opticalwiring for supplying a clock, a skew at the time of dividing a clocksignal to a plurality of light receiving portions can be almostsuppressed.

Third Embodiment

FIG. 9 is a schematic sectional view of a photoelectronic deviceaccording to the third embodiment of the present invention.

A plurality of semiconductor chips (10 a and 10 b) are adhered to anoptical waveguide sheet 30 and mounted on an interposer 60. Also, alight emitting element 20 is also mounted on the interposer 60, and itis configured that a light from the light emitting element 20 isirradiated to the core from a side surface of the optical waveguidesheet 30. Other configuration than that is substantially the same asthat in the first embodiment.

In the photoelectronic device of the present embodiment, it can beconfigured that the plurality of semiconductor chips are respectivelyprovided with light receiving portions, and each of the light receivingportions is connected to each of lights divided at the optical waveguidesheet.

Furthermore, it may be configured that a part or all of the plurality ofsemiconductor chips is provided with a plurality of light receivingportions, and each of the light receiving portions is connected to eachof the lights divided at the optical waveguide sheet.

For example, the first semiconductor chip 10 a is formed with aplurality of light receiving portions 11 a, which are opticallyconnected by mirror surfaces (MRa and MRb) provided on the opticalwaveguide sheet.

On the other hand, the second semiconductor chip 10 b is formed with aplurality of light receiving portions 11 b, which are opticallyconnected by mirror surfaces (MRc and MRd) provided on the opticalwaveguide sheet.

Also, for example, by configuring that the light emitting element 20 isconnected to a cooling body 23 and provided with a thermal via TVpenetrating through the interposer, reliability of the photoelectronicdevice can be improved.

It can be produced by holding the optical waveguide sheet with the lightemitting side facing upward, successively mounting the semiconductorchip by aligning the light emitting portion with positions of the lightreceiving portions on the semiconductor chip via an adhesive sheet,furthermore, providing pad opening portions reaching to the pads of thesemiconductor chip, and mounting on the interposer via the bumps.

According to the photoelectronic device according to the above presentembodiment, it is configured that the optical waveguide sheet fordividing a clock and the semiconductor chip are put together, andcapable of maintaining the degree of freedom in designing for dealingwith design changes and responding to producing a variety of kinds insmall amounts. Particularly, by attaining completely equal-length wiringin optical wiring for supplying a clock, a skew at the time of dividinga clock signal to a plurality of light receiving portions can be almostsuppressed.

According to the photoelectronic device according to the above presentembodiment, a problem of a clock skew caused when the semiconductor chipbecomes high at speed is solved, an erroneous operation can beprevented, timing analysis of a clock requiring a long time in thedesigning means of the related art becomes unnecessary, and the designdevelopment period can be widely reduced.

Also, as in the production methods of the photoelectronic devices in therespective embodiments, by producing the optical waveguide sheetseparately, a mechanism of supplying a very inexpensive clock very fastcan be realized comparing with the case of the related art, wherein anoptical waveguide is formed on a semiconductor chip every time.

It is possible to flexibly respond to design changes of a semiconductorchip, and convenience and reusability particularly in a stage ofdeveloping prototypes of a number of kinds in small amounts are veryhigh.

Also, a branch in the photoelectronic devices of the respectiveembodiments is different from a Y-shaped guiding branch and has no limiton bending, so that a clock without a skew can be supplied to manypoints as up to 6 branches to 10 branches (64 to 1024 in points) or soon an LSI of about 10 mm×10 mm.

The photoelectronic device of the present embodiment can be used forcomputer apparatuses, particularly, MPU or an image processing processorrequiring a large capacity and signal processing at a high speed, suchas a game computer, network server, home server and brain of a robot,and ultrahigh-speed signal processing LSI, such as a high-speed cashmemory.

The present invention is not limited to the above explanation.

For example, as a semiconductor chip to be put together with the opticalwaveguide sheet, a SiP (Systems-in-package semiconductor device) can beused and, for example, a package combining a semiconductor chip havingan active element, such as a transistor, and a passive element, such asan inductance, capacitor or electric resistance element, can be used.

As an optical device incorporated in a SiP, light emitting diode, etc.can be used other than laser diode.

Other than the above, a variety of modifications can be made within thescope of the present invention.

The photoelectronic device of the present invention can be applied to aphotoelectronic device configured that a light emitting element foremitting a light to be a clock signal and a semiconductor chip having anelectron circuit including a light receiving portion are opticallyconnected by an optical waveguide sheet.

The production method of the photoelectronic device of the presentinvention can be applied to produce a photoelectronic device configuredthat a light emitting element for emitting a light to be a clock signaland a semiconductor chip having an electron circuit including a lightreceiving portion are optically connected by an optical waveguide sheet.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alternations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A photoelectronic device, comprising: a light emitting element foremitting a light to be a clock signal; a semiconductor chip providedwith light receiving portions for receiving said light; and an opticalwaveguide sheet formed to be a sheet, wherein an outer circumference ofa core is covered with a clad, and adhered to said semiconductor chip;wherein said optical waveguide sheet is irradiated at a light incidentportion of said core with said light from said light emitting element;said optical waveguide sheet is provided with one or more T-shapedbranch, and at each T-shaped branch is provided with a vertical openingportion having a vertical inner wall being vertical with respect to thedirection within a surface of said optical waveguide sheet, and saidvertical inner wall serves as a mirror surface for dividing, reflectingand guiding said light to two different directions; and a slopingopening portion having a sloping inner wall having an inclination withthe optical waveguide direction of said core is provided at a positionof connecting each of said divided lights to each of said lightreceiving portions, and said sloping inner wall serves as a mirrorsurface for reflecting said light to the direction being out of thesurface of said optical waveguide sheet to be connected to said lightreceiving portion.
 2. A photoelectronic device as set forth in claim 1,wherein in said optical waveguide sheet, distances from a position of alight incident portion of said core to positions of respectivelyconnecting said lights to said light receiving portions are equal in allpaths that the lights divided to two or more are guided.
 3. Aphotoelectronic device as set forth in claim 1, wherein said slopinginner wall of said sloping opening portion has an inclination of about45° with respect to the optical waveguide direction of said core.
 4. Aphotoelectronic device as set forth in claim 1, wherein saidsemiconductor chip is provided with a plurality of said light receivingportions; and said lights divided at said optical waveguide sheet areconnected to said respective light receiving portions.
 5. Aphotoelectronic device as set forth in claim 1, comprising a pluralityof said semiconductor chips; and said lights divided at said opticalwaveguide sheet are respectively connected to respective light receivingportions provided respectively to said plurality of semiconductor chips.6. A photoelectronic device as set forth in claim 5, wherein a part orall of said plurality of semiconductor chips is provided with aplurality of light receiving portions; and said lights divided at saidoptical waveguide sheet are respectively connected to said respectivelight receiving portions.
 7. A photoelectronic device as set forth inclaim 1, wherein said light emitting element is mounted on a surface ofsaid semiconductor chip on the side adhered to said optical waveguidesheet; and a light from said light emitting element irradiates said corefrom a side surface of said optical waveguide sheet.
 8. Aphotoelectronic device as set forth in claim 1, wherein saidsemiconductor chip adhered to said optical waveguide sheet and saidlight emitting element are mounted on an interposer; and a light fromsaid light emitting element irradiates said core from a side surface ofsaid optical waveguide sheet.
 9. A photoelectronic device as set forthin claim 8, wherein a plurality of said semiconductor chips are adheredto said optical waveguide sheet and mounted on said interposer.
 10. Aproduction method of a photoelectronic device for producing aphotoelectronic device including a light emitting element for emitting alight to be a clock signal, a semiconductor chip provided with lightreceiving portions for receiving said light, and an optical waveguidesheet for dividing said light to two or more and guiding the same to beconnected to said light receiving portions at positions of connecting tosaid light receiving portions, comprising the steps of: forming a firstclad on a dummy substrate, forming a core on said first clad to be apattern having one or more T-shaped branch, forming a second clad tocover said core, thereby forming an optical waveguide sheet formed to bea sheet wherein an outer circumference of the core is covered with theclad; forming at a position of said T-shaped branch on said opticalwaveguide sheet a vertical opening portion having a vertical inner wall,which is vertical with respect to the direction within the surface ofsaid optical waveguide sheet and becomes a mirror surface for dividingand reflecting said light to two different directions; forming at aposition of connecting said light to said light receiving portion onsaid optical waveguide sheet a sloping opening portion having a slopinginner wall, which has an inclination with the optical waveguidedirection of said core and becomes a mirror surface for reflecting saidlight to the direction being out of the surface of said opticalwaveguide sheet so as to be connected to said light receiving portion;releasing said optical waveguide sheet from said dummy substrate;aligning said optical waveguide sheet with said light receiving portionand adhering to said semiconductor chip; and mounting said lightemitting element by arranging the same, so that a light from said lightemitting element irradiates a light incident portion of said core.
 11. Aproduction method of a photoelectronic device as set forth in claim 10,wherein in the step of forming said optical waveguide sheet, the opticalwaveguide sheet is formed, so that distances of guiding said lights froma position of a light incident portion of said core to positions ofconnecting said respective lights to said light receiving portionsbecome equal in all paths that the lights divided to two or more areguided.
 12. A production method of a photoelectronic device as set forthin claim 10, further including the step of forming a release layer on asurface of said dummy substrate before the step of forming said opticalwaveguide sheet on said dummy substrate, wherein, in the step of formingsaid optical waveguide sheet, the optical waveguide sheet is formed onsaid release layer; and in the step of releasing said optical waveguidesheet from said dummy substrate, it is released on a boundary surface ofsaid optical waveguide sheet and said release layer.
 13. A productionmethod of a photoelectronic device as set forth in claim 12, whereinsaid release layer is a stacked body of a titanium layer and a copperlayer, or a silicon oxide layer.
 14. A production method of aphotoelectronic device as set forth in claim 10, wherein in the step offorming said sloping opening portion, said sloping inner wall of saidsloping opening portion is formed to have an inclination of about 45°with respect to the optical waveguide direction of said core.
 15. Aproduction method of a photoelectronic device as set forth in claim 10,wherein in the step of mounting said light emitting element, said lightemitting element is mounted on a surface of said semiconductor chip onthe side adhered to said optical waveguide sheet, so that a light fromsaid light emitting element irradiates said core from a side surface ofsaid optical waveguide sheet.
 16. A production method of aphotoelectronic device as set forth in claim 10, furthermore includingthe step of mounting said semiconductor chip adhered to said opticalwaveguide sheet on an interposer, wherein in the step of mounting saidlight emitting element, said light emitting element is mounted on saidinterposer, so that a light from said light emitting element irradiatessaid core from a side surface of said optical waveguide sheet.